Is there an answer in there somewhere?
Chile, low-contrast subjects like your black frogfish are a challenge. They generally make boring photos, even though a frogfish is very cool. I'd look to get as close as possible, eliminate any distracting elements in the composition, maximize my depth of field, and try lighting it from different angles and perhaps let the shadows outline the subject's form a little. Be sure to get the eyes in sharp focus—that'll help the viewer see an exotic fish rather than a formless blob.
Not a frogfish, but this subject presented many of the same challenges: